This article presents an equivalent circuit approach used for the modelling of a system consisting of an antenna and a RF/DC rectifying circuit (rectenna) at 2.45 GHz. The measurements and simulations steps used for parameter extraction and model validation are presented. The major interest in this approach is the ability to study a complete system of energy transmission in a single simulator environment. This method is illustrated in the case of a microwave transmission without any modulation, that is to say the derived model can be easily integrated. The results obtained using this simple example show a relatively good agreement with the experiment and can form the basis for further developments of more complex systems